首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   158101篇
  免费   13707篇
  国内免费   7924篇
电工技术   9745篇
技术理论   2篇
综合类   12518篇
化学工业   24634篇
金属工艺   8710篇
机械仪表   9607篇
建筑科学   11471篇
矿业工程   3405篇
能源动力   4497篇
轻工业   12931篇
水利工程   3190篇
石油天然气   6500篇
武器工业   1209篇
无线电   20144篇
一般工业技术   18681篇
冶金工业   7340篇
原子能技术   1986篇
自动化技术   23162篇
  2024年   486篇
  2023年   1965篇
  2022年   3886篇
  2021年   5486篇
  2020年   3963篇
  2019年   3420篇
  2018年   3780篇
  2017年   4340篇
  2016年   4059篇
  2015年   5692篇
  2014年   7595篇
  2013年   9519篇
  2012年   10690篇
  2011年   11782篇
  2010年   10622篇
  2009年   10362篇
  2008年   10295篇
  2007年   9872篇
  2006年   9556篇
  2005年   7920篇
  2004年   5930篇
  2003年   5131篇
  2002年   5678篇
  2001年   4924篇
  2000年   3875篇
  1999年   3333篇
  1998年   2721篇
  1997年   2323篇
  1996年   2090篇
  1995年   1772篇
  1994年   1354篇
  1993年   1077篇
  1992年   860篇
  1991年   657篇
  1990年   551篇
  1989年   402篇
  1988年   347篇
  1987年   248篇
  1986年   179篇
  1985年   178篇
  1984年   130篇
  1983年   96篇
  1982年   81篇
  1981年   77篇
  1980年   69篇
  1979年   49篇
  1978年   40篇
  1977年   43篇
  1976年   69篇
  1973年   24篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
53.
The synthesis and performance of a novel temperature-tolerant foamed resin for enhanced oil recovery were investigated using various methods, including infrared, NMR, scanning electron microscopy (SEM), and displacement experiments. Polycondensation of furfuryl alcohol prepolymers was confirmed by the infrared and NMR results. The poor temperature tolerance of furfuryl alcohol prepolymers after gelation at high temperatures is mainly due to the fracture of furan rings. The addition of ester additives is an effective method of increasing the temperature tolerance of the prepared foamed resins and can effectively reduce the weight-loss rate of the polycondensation products. The SEM results show that the skeleton structure of the foamed resin remains intact after high-temperature treatment. Thus, the novel plugging agent system has excellent thermal stability and still has a high strength (>0.8 MPa) after high-temperature aging treatment for 40 days, giving the prepared foamed resin a good plugging performance (plugging rate > 91%) at 250 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47161.  相似文献   
54.
Ionomics is a novel multidisciplinary field that uses advanced techniques to investigate the composition and distribution of all minerals and trace elements in a living organism and their variations under diverse physiological and pathological conditions. It involves both high-throughput elemental profiling technologies and bioinformatic methods, providing opportunities to study the molecular mechanism underlying the metabolism, homeostasis, and cross-talk of these elements. While much effort has been made in exploring the ionomic traits relating to plant physiology and nutrition, the use of ionomics in the research of serious diseases is still in progress. In recent years, a number of ionomic studies have been carried out for a variety of complex diseases, which offer theoretical and practical insights into the etiology, early diagnosis, prognosis, and therapy of them. This review aims to give an overview of recent applications of ionomics in the study of complex diseases and discuss the latest advances and future trends in this area. Overall, disease ionomics may provide substantial information for systematic understanding of the properties of the elements and the dynamic network of elements involved in the onset and development of diseases.  相似文献   
55.
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry  相似文献   
56.
57.
58.
59.
60.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号